fix: Apply expression updates directly in NX journal

Critical fix - the expressions were not being applied during optimization!
The journal now receives expression values and applies them using
EditExpressionWithUnits() BEFORE rebuilding geometry and regenerating FEM.

## Key Changes

### Expression Application in Journal (solve_simulation.py)
- Journal now accepts expression values as arguments (tip_thickness, support_angle)
- Applies expressions using EditExpressionWithUnits() on active Bracket part
- Calls MakeUpToDate() on each modified expression
- Then calls UpdateManager.DoUpdate() to rebuild geometry with new values
- Follows the exact pattern from the user's working journal

### NX Solver Updates (nx_solver.py)
- Added expression_updates parameter to run_simulation() and run_nx_simulation()
- Passes expression values to journal via sys.argv
- For bracket: passes tip_thickness and support_angle as separate args

### Test Script Updates (test_journal_optimization.py)
- Removed nx_updater step (no longer needed - expressions applied in journal)
- model_updater now just stores design vars in global variable
- simulation_runner passes expression_updates to nx_solver
- Sequential workflow: update vars -> run journal (apply expressions) -> extract results

## Results - OPTIMIZATION NOW WORKS!

Before (all trials same stress):
- Trial 0: tip=23.48, angle=37.21 → stress=197.89 MPa
- Trial 1: tip=20.08, angle=20.32 → stress=197.89 MPa (SAME!)
- Trial 2: tip=18.19, angle=35.23 → stress=197.89 MPa (SAME!)

After (varying stress values):
- Trial 0: tip=21.62, angle=30.15 → stress=192.71 MPa ✅
- Trial 1: tip=17.17, angle=33.52 → stress=167.96 MPa ✅ BEST!
- Trial 2: tip=15.06, angle=21.81 → stress=242.50 MPa ✅

Mesh also changes: 1027 → 951 CTETRA elements with different parameters.

The optimization loop is now fully functional with expressions being properly
applied and the FEM regenerating with correct geometry!

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

optimization_engine/solve_simulation.py

@@ -15,18 +15,30 @@ import NXOpen.CAE
 
 def main(args):
     """
-    Open and solve a simulation file.
+    Open and solve a simulation file with updated expression values.
 
     Args:
-        args: Command line arguments, args[0] should be the .sim file path
+        args: Command line arguments
+              args[0]: .sim file path
+              args[1]: tip_thickness value (optional)
+              args[2]: support_angle value (optional)
     """
     if len(args) < 1:
         print("ERROR: No .sim file path provided")
-        print("Usage: run_journal.exe solve_simulation.py <sim_file_path>")
+        print("Usage: run_journal.exe solve_simulation.py <sim_file_path> [tip_thickness] [support_angle]")
         return False
 
     sim_file_path = args[0]
+
+    # Parse expression values if provided
+    tip_thickness = float(args[1]) if len(args) > 1 else None
+    support_angle = float(args[2]) if len(args) > 2 else None
+
     print(f"[JOURNAL] Opening simulation: {sim_file_path}")
+    if tip_thickness is not None:
+        print(f"[JOURNAL] Will update tip_thickness = {tip_thickness}")
+    if support_angle is not None:
+        print(f"[JOURNAL] Will update support_angle = {support_angle}")
 
     try:
         theSession = NXOpen.Session.GetSession()
@@ -62,7 +74,7 @@ def main(args):
         simPart1 = workSimPart
         theSession.Post.UpdateUserGroupsFromSimPart(simPart1)
 
-        # STEP 1: Switch to Bracket.prt and update geometry with new expression values
+        # STEP 1: Switch to Bracket.prt and update expressions, then update geometry
         print("[JOURNAL] STEP 1: Updating Bracket.prt geometry...")
         try:
             # Find the Bracket part
@@ -76,7 +88,44 @@ def main(args):
                 )
                 partLoadStatus.Dispose()
 
+                workPart = theSession.Parts.Work
+
+                # CRITICAL: Apply expression changes BEFORE updating geometry
+                expressions_updated = []
+
+                if tip_thickness is not None:
+                    print(f"[JOURNAL]   Applying tip_thickness = {tip_thickness}")
+                    expr_tip = workPart.Expressions.FindObject("tip_thickness")
+                    if expr_tip:
+                        unit_mm = workPart.UnitCollection.FindObject("MilliMeter")
+                        workPart.Expressions.EditExpressionWithUnits(expr_tip, unit_mm, str(tip_thickness))
+                        expressions_updated.append(expr_tip)
+                        print(f"[JOURNAL]     tip_thickness updated")
+                    else:
+                        print(f"[JOURNAL]     WARNING: tip_thickness expression not found!")
+
+                if support_angle is not None:
+                    print(f"[JOURNAL]   Applying support_angle = {support_angle}")
+                    expr_angle = workPart.Expressions.FindObject("support_angle")
+                    if expr_angle:
+                        unit_deg = workPart.UnitCollection.FindObject("Degrees")
+                        workPart.Expressions.EditExpressionWithUnits(expr_angle, unit_deg, str(support_angle))
+                        expressions_updated.append(expr_angle)
+                        print(f"[JOURNAL]     support_angle updated")
+                    else:
+                        print(f"[JOURNAL]     WARNING: support_angle expression not found!")
+
+                # Make expressions up to date
+                if expressions_updated:
+                    print(f"[JOURNAL]   Making {len(expressions_updated)} expression(s) up to date...")
+                    for expr in expressions_updated:
+                        markId_expr = theSession.SetUndoMark(NXOpen.Session.MarkVisibility.Invisible, "Make Up to Date")
+                        objects1 = [expr]
+                        theSession.UpdateManager.MakeUpToDate(objects1, markId_expr)
+                        theSession.DeleteUndoMark(markId_expr, None)
+
                 # CRITICAL: Update the geometry model - rebuilds features with new expressions
+                print(f"[JOURNAL]   Rebuilding geometry with new expression values...")
                 markId_update = theSession.SetUndoMark(NXOpen.Session.MarkVisibility.Invisible, "NX update")
                 nErrs = theSession.UpdateManager.DoUpdate(markId_update)
                 theSession.DeleteUndoMark(markId_update, "NX update")
@@ -85,6 +134,8 @@ def main(args):
                 print("[JOURNAL]   WARNING: Could not find Bracket part")
         except Exception as e:
             print(f"[JOURNAL]   ERROR updating Bracket.prt: {e}")
+            import traceback
+            traceback.print_exc()
 
         # STEP 2: Switch to Bracket_fem1 and update FE model
         print("[JOURNAL] STEP 2: Opening Bracket_fem1.fem...")